Crosslink Agents and Dual Radical Cure Polymer

ABSTRACT

A synthetic route to polymers comprised of at least two monomers each with a very different reactivity ratio by using a corresponding crosslink agent for each monomer. Novel crosslink agents are described that provide for the copolymerization of at least one hydrophilic monomer with at least one lens monomer typically used to prepare materials for ophthalmic lenses. The new crosslink agents have a relatively high selectivity for the hydrophilic monomer and limited reactivity with the crosslink agent used to polymerize the lens monomer.

CROSS-REFERENCE

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.provisional application Ser. No. 60/948,850 filed Jul. 10, 2007, theentire disclosure of which is incorporated herein by reference.

The present invention relates to crosslink agents and the use of thecrosslink agents to provide a polymer. The polymer comprises monomericunits of two or more monomers and two or more crosslink agents. Thepolymer can be used as an optical polymeric material for an ophthalmiclens.

BACKGROUND OF THE INVENTION

Hydrogel contact lens materials prepared with N-vinyl-2-pyrrolidone(NVP) are expected to have a relatively high water content, and thus, anacceptable level of oxygen permeability. For example, NVP is oftencopolymerized with an alkyl acrylate or methacrylate such as methylmethacrylate to provide lens materials that typically have a watercontent of 50% to 80% by weight. However, such copolymers are difficultto synthesize in a homogeneous controlled manner because of thedifference in the polymerization reaction rates between the N-vinylgroups of NVP and the acryloyl or methacryloyl groups of the alkylacrylate or methacrylate. One typically observes a phase separation anda corresponding decrease in the transparency of the polymeric lensmaterial, or the mechanical properties of the lens material deterioratesas the lens absorbs water.

In an attempt to overcome the differences between NVP and the alkylacrylates/methacrylates, U.S. Pat. No. 4,547,543 describes the use ofN-methyl-3-methylene-2-pyrrolidone (NMMP). It is stated that NMMP has apolymerization reaction rate more in-line with acrylate/methacrylatemonomers, and still provides the necessary hydrophilic character desiredof NVP. Accordingly, the '543 patent describes a copolymer consistingessentially of: (a) from 50 to 95 parts by weight of the total monomerunits, of which, 25 to 100 parts is NMMP and 0 to 75 parts NVP; and (b)from about 5 to about 50 parts, by weight of the total monomer units, ofreinforcing monomer units consisting essentially of at least one monomerselected from the group consisting of alkyl acrylates, alkylmethacrylates, styrene, alkyl styrenes, benzyl acrylate and benzylmethacrylate.

U.S. Pat. No. 3,949,021 describes a somewhat different approach to theabove mentioned problem. The '021 patent describes trapping orencapsulating an already formed, water insoluble polymer (e.g.,poly(methyl methacrylate), polystyrene, or poly(vinyl acetate) inpoly(NVP). Also, U.S. patents by McCabe et al. (U.S. Pat. No. 6,822,016and U.S. Pat. No. 7,052,131) describe a process of making a polymeric,ophthalmic lens material from a high molecular weight hydrophilicpolymer and a silicone monomer. The McCabe process polymerizes thesilicon monomer in the presence of an already formed hydrophilicpolymer, e.g., poly(NVP) having a molecular weight of no less than about100,000 Daltons.

Conventional polymer formulations that include two or more free-radical,monomers with two very different reactivity ratios and a singlecrosslinking agent can provide a polymer in which the two monomerscoexist as essentially two homopolymers. During the initial stages ofthe polymerization reaction one monomer preferentially reacts with thecrosslink agent, and only after that monomer is nearly consumed does thesecond monomer begin to react with the crosslink agent. In someinstances, the large difference in the reactivity ratios of thecrosslink agent and the second monomer can provide a polymer withrelatively large amounts of unreacted second monomer or oligomer, whichthen must be extracted from the polymer. This is very inefficient interms of production cost (yields) and can be detrimental to the materialproperties. Also, it is often difficult to prepare a polymer from oneproduction batch to another and stay within design specifications undersuch variable reaction conditions.

The theoretical composition of the polymer formed by the reaction of twodifferent monomers (one of which is a crosslink agent) is determined bythe following:

dn ₁ /dn ₂=(N ₁ /N ₂)(r ₁ N ₁ +N ₂)/(r ₂ N ₂ +N ₁)

where n₁ is the moles of monomer 1 in the copolymer, n₂ is the moles ofmonomer 2 in the copolymer, N₁ and N₂ are the number of moles ofmonomers 1 and 2, respectively, in the monomer mixture, and r₁ and r₂are the monomer reactivity ratios. The reactivity ratios are defined interms of propagation rate constants, k₁₁, k₁₂, k₂₂ and k₂₁, according tothe following polymerization reactions.

M ₁ *+M ₁ →M ₁ M ₁ *k ₁₁

M ₁ *+M ₂ →M ₁ M ₂ *k ₁₂

M ₂ *+M ₂ →M ₂ M ₂ *k ₂₂

M ₂ *+M ₁ →M ₂ M ₁ *k ₂₁,

and r₁=k₁₁/k₁₂ and r₂=k₂₂/k₂₁.

The invention overcomes the shortcomings that result from attempts tocopolymerize at least two monomers with a single crosslink agent if oneof the two monomers has a very different reactivity ratio relative tothe crosslink agent.

SUMMARY OF THE INVENTION

The invention is directed to crosslink agents of general formula I

wherein R¹, R², R³, R⁴, R⁷ and R⁸ are independently selected fromhydrogen, C₁-C₄alkyl, C₁-C₂alkanol or hydroxyl;

A is O, O(CH₂CH₂O)_(v) or [SiR⁵R⁶O]_(w)SiR⁵R⁶, wherein R⁵ and R⁶ areindependently selected from C₁-C₄alkyl or phenyl, and v is from 1-20 andw is from 0 to 60;

m and n are integers independently selected from 1 to 10; p is 0 or 1;and q is an integer from 0 to 6; and

-   -   X and Y are independently selected from O or NR⁹, wherein R⁹ is        hydrogen, C₁-C₄alkyl or C₁-C₂alkanol.

The invention is also directed to crosslink agents of general formula II

wherein R¹, R², R³, R⁴, R⁷ and R⁸ are independently selected fromhydrogen, C₁-C₄alkyl, C₁-C₂alkanol or hydroxyl;

A is O, O(CH₂CH₂O)_(v) or [SiR⁵R⁶O]_(w)SiR⁵R⁶, wherein R⁵ and R⁶ areindependently selected from C₁-C₄alkyl or phenyl, and v is from 1-20 andw is from 0 to 60;

m and n are integers independently selected from 1 to 10; p is 0 or 1;and q is an integer from 0 to 6.

The invention is also directed to a polymer comprising the reactionproduct of two or more crosslink agents, a hydrophilic monomer and alens monomer, and at least one of the crosslink agents is of generalformula I or general formula II. The polymers can be used to form anophthalmic lens.

The invention is also directed to a polymer prepared with crosslinkagents of general formula III. The polymer is the reaction product oftwo or more crosslink agents, a hydrophilic monomer and a lens monomer,and at least one of the crosslink agents is of general formula III.

wherein R¹ and R² are independently selected from hydrogen, C₁-C₄alkyl,C₁-C₂alkanol or hydroxyl;

A is O, O(CH₂CH₂O)_(v) or [SiR⁵R⁶O]_(w)SiR⁵R⁶, wherein R⁵ and R⁶ areindependently selected from C₁-C₄alkyl or phenyl, and v is from 1-20 andw is from 0 to 60;

m is 1, 2 or 3; n and n′ are integers independently selected from 1 to10; and p is 0 or 1.

The invention is also directed to a polymer prepared by a process ofproviding a polymerization mixture that comprises a hydrophilic monomerthat has a reactivity ratio R_(h)=k_(hh)/k_(hx) and a crosslink agentthat has a reactivity ratio R_(x)=k_(hh)/k_(xh), wherein k_(hh), k_(hx),k_(xx) and k_(xh) are the propagation constants for the followingradical polymerization reactions, and M_(h) represents the hydrophilicmonomer, M_(h)* represents the hydrophilic monomer radical, M_(x)represents the crosslink agent, and M_(x)* represents the crosslinkagent radical,

M _(h) *+M _(h) →M _(h) M _(h) *k _(hh);

M _(h) *+M _(x) →M _(h) M _(x) *k _(hx);

M _(x) +M _(x) →M→M _(v) *k _(xx);

M _(x) *+M _(h) →M _(x) M _(h) *k _(xh); and

the ratio R_(h)/R_(x) is from 0.1 to 10. The polymerization alsocomprises a lens monomer that has a reactivity ratio R_(l)=k_(ll)/k_(ly)and a crosslink agent that has a reactivity ratio R_(y)=k_(yy)/k_(yl),wherein k_(ll), k_(ly), k_(yy) and k_(yl) are the propagation constantsfor the following radical polymerization reactions, and M_(l) representsthe lens monomer, M_(l)* represents the lens monomer radical, M_(y)represents the crosslink agent, and M_(y)* represents the crosslinkagent radical,

M _(l) *+M _(l) →M _(l) M _(l) *k _(ll);

M _(l) *+M _(y) →M _(l) M _(y) *k _(ly);

M _(y) *+M _(y) M _(y) M _(y) *k _(yy);

M _(y) *+M _(l) →M _(y) M ₁ *k _(yl); and

the ratio R_(l)/R_(y) is from 0.1 to 10. The resulting polymer can beused to form an ophthalmic lens.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a synthetic route to polymers comprised of atleast two monomers, and in particular, at least two vinyl monomers, eachwith a very different reactivity ratio by using a correspondingcrosslink agent for each monomer. Novel crosslink agents are describedthat allow one to copolymerize at least one hydrophilic monomer, e.g.,any N-vinyl lactam, with at least one conventional monomer typicallyused to prepare polymeric materials for ophthalmic lenses. Hereafter, wewill refer to a conventional monomer, some of which are described below,as a “lens monomer”. The new crosslink agents have a relatively highselectivity for the hydrophilic monomer and limited reactivity with thecrosslink agent used to polymerize the lens monomer.

The invention is also directed to a method of making a hydrophiliccrosslinked polymer that comprises at least two monomeric units and atleast two different crosslink units. Again, the two different crosslinkagents are required because the at least one hydrophilic monomer and theat least one lens monomer do not readily copolymerize. The use of acorresponding crosslink agent for each of the hydrophilic monomer andthe lens monomer ensures a mutually compatible polymer. As a result, theamount of hydrophilic monomer or hydrophilic oligomer that isextractable following the polymerization reaction is significantlyreduced. The use of the dual crosslink system also provides a route tobetter control the final chemical, physical and structuralcharacteristics of the resulting polymer.

The invention is directed to crosslink agents of general formula I

wherein R¹, R², R³, R⁴, R⁷ and R⁸ are independently selected fromhydrogen, C₁-C₄alkyl, C₁-C₂alkanol or hydroxyl;

A is O, O(CH₂CH₂O)_(v) or [SiR⁵R⁶O]_(w)SiR⁵R⁶, wherein R⁵ and R⁶ areindependently selected from C₁-C₄alkyl or phenyl, and v is from 1-20 andw is from 0 to 60;

m and n are integers independently selected from 1 to 10; p is 0 or 1;and q is an integer from 0 to 6; and

X and Y are independently selected from O or NR⁹, wherein R⁹ ishydrogen, C₁-C₄alkyl or C₁-C₂alkanol.

The terms “straight or branched alkyl” and “cyclic hydrocarbon” arealiphatic radicals that can include one or more non-carbon substituentgroups, e.g., hydroxyl, amine, carboxy acid, ester or ether.

In one embodiment, Y is NR⁹ and X is O. In another embodiment, Y is Oand X is NR⁹. In still another embodiment, Y is NR⁹ and X is NR⁹. In aparticular embodiment, m and n are 2 or 3, p is 0, and R¹, R², R³ and R⁴are hydrogen. Also, it is preferred that q is 0, 1 or 2.

The invention is also directed to crosslink agents of general formula II

wherein R¹, R², R³, R⁴, R⁷ and R⁸ are independently selected fromhydrogen, C₁-C₄alkyl, C₁-C₂alkanol or hydroxyl;

A is O, O(CH₂CH₂O)_(v) or [SiR⁵R⁶O]_(w)SiR⁵R⁶, wherein R⁵ and R⁶ areindependently selected from C₁-C₄alkyl or phenyl, and v is from 1-20 andw is from 0 to 60;

m and n are integers independently selected from 1 to 10; p is 0 or 1;and q is an integer from 0 to 6.

In a particular embodiment, m and n are 2 or 3, p is 0, and R¹, R², R³and R⁴ are hydrogen. Also, it is preferred that q is 0, 1 or 2.

The invention is also directed to a polymer comprising the reactionproduct of two or more crosslink agents, a hydrophilic monomer and alens monomer, and at least one of the crosslink agents is of generalformula I or general formula II. The polymers can be used to form anophthalmic lens.

The invention is also directed to a polymer prepared with crosslinkagents of general formula III. The polymer is the reaction product oftwo or more crosslink agents, a hydrophilic monomer and a lens monomer,wherein at least one of the crosslink agents is of general formula III.

wherein R¹ and R² are independently selected from hydrogen, C₁-C₄alkyl,C₁-C₂alkanol or hydroxyl;

A is O, O(CH₂CH₂O)_(v) or [SiR⁵R⁶O]_(w)SiR⁵R⁶, wherein R⁵ and R⁶ areindependently selected from C₁-C₄alkyl or phenyl, and v is from 1-20 andw is from 0 to 60;

m is 1, 2 or 3; n and n′ are integers independently selected from 1 to10; and p is 0 or 1.

For example, in one embodiment, m=1, R¹ and R² is hydrogen, n an n′ areindependently 3, 4 or 5, and p=0.

The described method of copolymerizing a hydrophilic monomer with a lensmonomer in the presence of a crosslink agent of general formula I,general formula II or general formula III provides certain advantages ifthe hydrophilic monomer is a N-vinyl lactam, particularly a N-vinyllactam selected from the group consisting of N-vinyl pyrrolidone,N-vinyl piperidone and N-vinyl-ε-caprolactam, and mixtures thereof. The

N-vinyl lactams are known to be notoriously sluggish in free radicalpolymerization reactions with many of the more common acrylate-,methacrylate- or acrylamide-based monomers. Particularly, thoseacrylate-, methacrylate- or acrylamide-based monomers typically used toprovide polymer materials for ophthalmic lenses such as 2-hydroxyethylmethacrylate (HEMA), tris-(trimethylsiloxy)-3-methacryloxypropylsilane(TRIS), dimethylacrylamide (DMA), ethylene glycol dimethacrylate(EGDMA), methacrylic acid (MA), 2-phenylethyl acrylate, 2-phenoxyethylacrylate, 2-phenoxyethyl methacrylate, triethylene glycoldimethacrylate, tetraethylene glycol dimethacrylate, isobornylmethacrylate, 2-methoxyethyl methacrylate, glycerol methacrylate,monomethoxy polyethyleneglycol (PEG) methacrylate.

For example, previous attempts to copolymerize NVP with any one or moreof the lens monomers listed above invariably results in formation of anacrylate, a methacrylate or an acrylamide polymer with very little NVPincorporation. Instead, most of the NVP present in the polymer ispresent as non-covalently attached homopolymer chains of poly(NVP).These poly(NVP) chains tend to leach out from the polymer over time. Theleaching of the poly(NVP) reduces the hydrophilic character of thepolymer, and a reduction in water content or wettability is observedwith the polymer. Moreover, attempts to copolymerize NVP with one ormore siloxane macromonomers described below can lead to a phaseseparation, and in the case of an ophthalmic lens such phase separationcan lead to opacification of the material.

Table 1 lists the reactivity ratios for NVP (monomer 1) and some of themore monomers (monomer 2) typically used to make ophthalmic lensmaterials. These reactivity ratios are taken from J. Brandrup and E. J.Immergut, “Polymer Handbook”, 3^(rd) Ed. Wiley Interscience (1989).

TABLE 1 Reactivity Ratios for NVP. monomer 2 r₁ r₂ 2-hydroxyethylmethacrylate −0.019 4.841 styrene 0.057 17.20 methyl methacrylate 0.0104.04 vinyl cyclohexyl ether 1.91 −0.110 vinyl isopropyl ether 0.8700.030 vinyl butyl ether 1.49 0 vinyl benzoate 2.507 0.408 vinyl acetate0.340 0.195 N-vinyl caprolactam 2.8 1.7 N-vinyl-t-butyl carbamate 0.42.4 AMPS 0.13 0.66 AMPS: 2-Acrylamido-2-methyl-1-propanesulfonic acidsodium salt:

The method of the invention is particularly useful to copolymerize apolymerization mixture that comprises a hydrophilic monomer that has areactivity ratio R_(h)=k_(hh)/k_(hx) and a crosslink agent that has areactivity ratio R_(x)=k_(xx)/k_(xh), wherein k_(hh), k_(hx), k_(xx) andk_(xh) are the propagation constants for the following radicalpolymerization reactions, and M_(h) represents the hydrophilic monomer,M_(h)* represents the hydrophilic monomer radical, M_(x) represents thecrosslink agent, and M_(x)* represents the crosslink agent radical,

M _(h) *+M _(h) →M _(h) M _(h) *k _(hh);

M _(h) *+M _(x) →M _(h) M _(x) *k _(hx);

M _(x) *+M _(x) →M _(x) M _(v) *k _(xx);

M _(x) *+M _(h) →M _(x) M _(h) *k _(xh); and

the ratio R_(h)/R_(x) is from 0.1 to 10. The polymerization alsocomprises a lens monomer that has a reactivity ratio R_(l)=k_(ll)/k_(ly)and a crosslink agent that has a reactivity ratio R_(y)=k_(yy)/k_(yl),wherein k_(ll), k_(ly), k_(yy) and k_(yl) are the propagation constantsfor the following radical polymerization reactions, and M_(l) representsthe lens monomer, M_(l)* represents the lens monomer radical, M_(y)represents the crosslink agent, and M_(y)* represents the crosslinkagent radical,

M _(l) *+M _(l) →M _(l) M _(l) *k _(ll);

M _(l) *+M _(y) →M _(l) M _(y) *k _(ly);

M _(y) *+M _(y) →M _(y) M _(y) *k _(yy);

M _(y) *+M _(l) →M _(y) M _(l) *k _(yl); and

the ratio R_(l)/R_(y) is from 0.1 to 10. The resulting polymer can beused to form an ophthalmic lens.

In the preparation of many of the polymerization mixtures thehydrophilic monomer and the lens monomer will typically have arelatively large reactivity difference. In other words, if one were todefine a reactivity ratio, R_(H)/R_(L), based on a similar set ofpolymerization reactions shown below (the crosslink agent being thesame—a single crosslink system), the reactivity ratio should be large,i.e., a 10-fold difference (e.g., greater than 10 or less than 0.1).Accordingly, the hydrophilic monomer and the lens monomer have areactivity ratio, R_(H)/R_(L), greater than 10 or less than 0.1, thereactivity ratio, R_(H)/R_(L), is defined the following radicalpolymerization reactions, wherein M_(h) represents the hydrophilicmonomer, M_(h)* represents the hydrophilic monomer, M_(l) represents thelens monomer, M_(l)* represents the lens monomer radical, M_(l)represents the crosslink agent, and M_(i)* represents the crosslinkagent radical,

M _(h) *+M _(h) →M _(h) M _(h) *k _(hh);

M _(h) *+M _(i) →M _(h) M _(i) *k _(hi);

M _(i) *+M _(i) →M _(i) M _(i) *k _(ii);

M _(i) *+M _(h) →M _(i) M _(h) *k _(ih); and R_(H) is R_(h)/R_(i),

and

M _(l) *+M _(l) →M _(l) M _(l) *k _(ll);

M _(l) *+M _(i) →M _(l) M _(i) *k _(li);

M _(i) *+M _(i) →M _(i) M _(i) *k _(ii);

M _(i) *+M _(l) →M _(i) M _(l) *k _(il); and R_(L) is R_(l)/R_(i).

Accordingly, in one embodiment, the hydrophilic monomer is a N-vinyllactam selected from the group consisting of N-vinyl pyrrolidone,N-vinyl piperidone and N-vinyl-ε-caprolactam and mixtures thereof. Othersuitable hydrophilic vinyl monomers include N-vinylimidazolidone,N-vinylsuccinimide and N-vinylforamide. In many instances, however, thehydrophilic monomer will be N-vinyl pyrrolidone.

Exemplary lens monomers that are copolymerized with the one or morehydrophilic monomers include acrylate-, methacrylate- oracrylamide-based monomers. Particularly, those acrylate-, methacrylate-or acrylamide-based monomers typically used to provide polymer materialsfor ophthalmic lenses such as HEMA, TRIS, DMA, EGDMA, MA, 2-phenylethylacrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate,triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate,isobornyl methacrylate, 2-methoxyethyl methacrylate, glycerolmonomethacrylate, monomethoxy polyethyleneglycol (PEG) methacrylates

The described method is also particularly useful for the preparation ofpolymeric silicon hydrogels. In this instance, one or more siloxanemonomers or macromonomers described below are polymerized with thehydrophilic monomer. In some instances, there can be an advantage ofinserting a siloxane linkage in the crosslink agent, that is, A is[SiR⁵R⁶O]_(v)SiR⁵R⁶ and p is 1 according to general formula I or ofgeneral formula II, for the synthesis of a silicon hydrogel.

1. The Use of the Crosslinking Agent to Make Contact Lens Materials.

Any one or more of known silicon-containing monomers or macromonomerscan be combined with the hydrophilic monomer and a crosslink agent ofgeneral formula I, general formula II or general formula III to providea monomer mixture that is then polymerized to provide a siloxane polymerfor the manufacture of an ophthalmic lens material.

A particular silicon monomer that can be used is of Structure A.

wherein R^(i) is H or CH₃, q is 1 or 2 and for each q, R^(l), R^(m) andR^(n) are independently selected from ethyl, methyl, benzyl, phenyl or amonovalent siloxane chain comprising from 1 to 30 repeating Si—O units,p is an integer from 1 to 10, r=(3−q), X is O, NH or N(C₁₋₄alkyl), a is0 or 1, and L is a divalent linking group which preferably comprisesfrom 2 to 5 carbons, which may also optionally comprise ether orhydroxyl groups, for example, a poly(ethylene glycol) chain.

Examples of the silicone-containing monomers of Structure A that can beused are (3-methacryloyloxypropyl)bis(trimethylsiloxy)methylsilane,(3-methacryloyloxypropyl)-pentamethyldisiloxane,(3-methacryloyloxy-2-hydroxypropyloxy)bis(trimethylsiloxy)methylsilane.Preferred silicone-containing monomers aremonomethacryloyloxyalkyl-terminated polydimethylsiloxanes (“mPDMS”),such as those shown in structure B.

where b=0 to 100, and R^(k) is any C₁₋₁₀ aliphatic or aromatic groupwhich can include hetero atoms; provided that R^(k) is notfunctionalized at the point at which it is bonded to Si. Preferably,R^(k) is a C₃₋₈ alkyl groups with butyl groups, particularly sec-butylgroups, being most preferred. R^(j) is an ethylenically unsaturatedmoiety; preferably a single polymerizable vinyl group. More preferably,R^(j) is a methacryl moiety but it can also be an acryl or styrenicmoiety or other similar moiety.

Other silicon-containing monomers that can be used include(3-methacryloxypropyl)tris(trimethylsiloxy)silane (TRIS), amide analogsof TRIS described in U.S. Pat. No. 4,711,943, and the vinylcarbamate orcarbonate analogs described in U.S. Pat. No. 5,070,215.

Examples of some other silicon-containing monomers include bulkypolysiloxanylalkyl(meth)acrylic monomers. An example of bulkypolysiloxanylalkyl (meth)acrylic monomers are represented by StructureC:

wherein X denotes O or NR^(i); h is an integer from 1 to 10;

each R^(i) independently denotes hydrogen or methyl; and each R^(p)independently denotes a lower alkyl radical, phenyl radical or a grouprepresented by

wherein each R^(q) independently denotes a lower alkyl or phenylradical.

Another class of representative silicon-containing monomers includessilicone-containing vinyl carbonate or vinyl carbamate monomers such as:

-   1,3-bis[4-vinyloxycarbonyloxy)but-1-yl]tetramethyldisiloxane;-   1,3-bis[4-vinyloxycarbonyloxy)but-1-yl]polydimethylsiloxane;-   3-(trimethylsilyl)propyl vinyl carbonate;-   3-(vinyloxycarbonylthio)propyl-[tris(trimethylsiloxy)silane];-   3-[tris(trimethylsiloxy)silyl]propyl vinyl carbamate;-   3-[tris(trimethylsiloxy)silyl]propyl allyl carbamate;-   3-[tris(trimethylsiloxy)silyl]propyl vinyl carbonate;-   t-butyldimethylsiloxyethyl vinyl carbonate;-   trimethylsilylethyl vinyl carbonate; and trimethylsilylmethyl vinyl    carbonate.

Examples of silicon-containing vinyl carbonate or vinyl carbamatemonomers are represented by Structure D:

wherein:

Y denotes O, S or NH;

R^(Si) denotes a silicone-containing organic radical;

R^(i) denotes hydrogen or methyl;

d is 1, 2, 3 or 4; and q is 0 or 1.

Suitable silicone-containing organic radicals R^(Si) include thefollowing: —(CH₂)_(n)Si[(CH₂)_(m)CH₃]₃; —(CH₂)_(n)Si[OSi(CH₂)_(m)CH₃]₃;—(CH₂)_(n)Si[OSi(R^(r))₃]₃—(CH₂)_(n)[Si(R^(r))₂O]_(e)Si(R^(r))₃; and—(CH₂)_(n)[Si(R^(r))₂O]_(e)M, wherein: M is represented by

wherein p is 1 to 6;

R^(r) denotes an alkyl radical or a fluoroalkyl radical having 1 to 6carbon atoms;

e is an integer from 1 to 200; n is 1, 2, 3 or 4; and m is 0, 1, 2, 3, 4or 5.

An example of a particular species within Structure D is represented byStructure E.

Another class of silicon-containing monomers includespolyurethane-polysiloxane macromonomers (also sometimes referred to asprepolymers), which may have hard-soft-hard blocks like traditionalurethane elastomers. Examples of silicone urethane monomers arerepresented by general Formulae IV and V:

E(*D*A*D*G)_(a)*D*A*D*E′; or  (IV)

E(*D*G*D*A)_(a)*D*G*D*E′;  (V)

wherein:

D denotes an alkyl diradical, an alkyl cycloalkyl diradical, acycloalkyl diradical, an aryl diradical or an alkylaryl diradical having6 to 30 carbon atoms;

G denotes an alkyl diradical, a cycloalkyl diradical, an alkylcycloalkyl diradical, an aryl diradical or an alkylaryl diradical having1 to 40 carbon atoms and which may contain ether, thio or amine linkagesin the main chain;

* denotes a urethane or ureido linkage;

a is at least 1;

A denotes a divalent polymeric radical of Structure F:

wherein:

each R^(r) independently denotes an alkyl or fluoro-substituted alkylgroup having 1 to 6 carbon atoms which may contain ether linkagesbetween carbon atoms;

m is at least 1; and

p is a number which provides a moiety weight of 400 to 10,000;

E denotes a polymerizable unsaturated organic radical represented byStructure G:

wherein:

R^(i) is hydrogen or methyl;

R^(t) is hydrogen, an alkyl radical having 1 to 6 carbon atoms, or a—CO—Y—R^(u) radical wherein Y is O, S or NH;

R^(s) is a divalent alkylene radical having 1 to 10 carbon atoms;

R^(u) is a alkyl radical having 1 to 12 carbon atoms;

X denotes CO or OCO;

Z denotes O or NH;

Ar denotes an aromatic radical having 6 to 30 carbon atoms;

w is an integer from 0 to 6; x is 0 or 1; y is 0 or 1; and z is 0 or 1.

An example of another silicon-containing monomer that can be combinedwith a silicone/epoxy-containing monomer are shown by Structure J

wherein B is represented by

and A is represented by

and wherein: R^(a) independently denote a C₁-C₆ alkyl; R^(b)independently denotes a C₁-C₆ alkylene; R^(c) independently denote alinear or branched alkylene; R^(d) independently denote a C₁-C₂alkylene; R^(e) independently denotes a C₁-C₆ alkylene; m and p areintegers independently selected form the integers from 3 to 44; and n isan integer from 13 to 80, and the silicon-containing monomer has anumber-average molecular weight of 2000 to 10,000.

A more specific example of a silicone-containing urethane monomer isrepresented by Structure H.

wherein m is at least 1 and is preferably 3 or 4, a is at least 1 andpreferably is 1, p is an integer which provides a moiety weight of 400to 10,000 and is preferably at least 30, R₁₀ is a diradical of adiisocyanate after removal of the isocyanate group, such as thediradical of isophorone diisocyanate, and each E″ is a group representedby:

The silicone hydrogels after hydration of the polymers will typicallycomprise from 10 to 60 weight percent water, or 25 to about 50 weightpercent water, of the total weight of the silicone hydrogel.

The silicon hydrogel materials can also be characterized as having lowhaze, good wettability and modulus. Haze is measured by placing testlenses in saline in a clear cell above a black background, illuminatingfrom below with a fiber optic lamp at an angle 66° normal to the lenscell, and capturing an image of the lens from above with a video camera.The background-subtracted scattered light image is quantitativelyanalyzed, by integrating over the central 10 mm of the lens, and thencompared to a −1.00 diopter CSI Thin Lens®, which is arbitrarily set ata haze value of 100, with no lens set as a haze value of 0.

Wettability is measured by measuring the dynamic contact angle or DCA at23° C. with borate buffered saline, using a Wilhelmy balance. Thewetting force between the lens surface and borate buffered saline ismeasured using a Wilhelmy microbalance while the sample is beingimmersed into or pulled out of the saline. The following equation isused

F=2γρ cos θ

where F is the wetting force, γ is the surface tension of the probeliquid, ρ is the perimeter of the sample at the meniscus and θ is thecontact angle. Typically, two contact angles are obtained from a dynamicwetting experiment, i.e., the advancing contact angle and the recedingcontact angle. The advancing contact angle is obtained from the portionof the wetting experiment where the sample is being immersed into thetest liquid. At least four lenses of each composition are measured andthe average is reported.

The silicon hydrogel materials have a modulus of at least about 30 psi,preferably from 30 psi to 110 psi, or between 40 psi and 70 psi. Modulusis measured by using the crosshead of a constant rate of movement typetensile testing machine equipped with a load cell that is lowered to theinitial gauge height. A suitable testing machine includes an Instronmodel 1122. A dog-bone shaped sample having a 0.522 inch length, 0.276inch “ear” width and 0.213 inch “neck” width is loaded into the gripsand elongated at a constant rate of strain of 2 in/min. until it breaks.The initial gauge length of the sample (Lo) and sample length at break(Lf) are measured. Twelve specimens of each composition are measured andthe average is reported. Tensile modulus is measured at the initiallinear portion of the stress/strain curve.

The silicon hydrogel materials have O₂ Dk values between 40 barrer and300 barrer, determined by the polarographic method. Lenses arepositioned on the sensor then covered on the upper side with a meshsupport. The lens is exposed to an atmosphere of humidified 21 wt %oxygen. The oxygen that diffuses through the lens is measured using apolarographic oxygen sensor consisting of a 4 mm diameter gold cathodeand a silver ring anode. The reference values are Balafilcon A lenses(Bausch & Lomb) which have a Dk value of about 80 barrer.

2. The Use of the Crosslinking Agent to Make Intraocular Lens Materials.

For application as an intraocular lens, polymeric materials are preparedwith the crosslink agent of general formula I, or of general formula II,a hydrophilic monomer and a lens monomer. The resulting polymer is ofsufficient optical clarity, and will have a relatively high refractiveindex of approximately 1.40 or greater.

An exemplary listing of lens monomers used to make intraocular lensesinclude: C₁-C₁₀ alkyl methacrylates (e.g., methyl methacrylate, ethylmethacrylate, propyl methacrylate, butyl methacrylate, octylmethacrylate, or 2-ethylhexyl methacrylate; C₁-C₁₀ alkyl acrylates(e.g., methyl acrylate, ethyl acrylate, propyl acrylate, n-butylacrylate, n-hexyl acrylate, 2-ethylhexyl acrylate or 2-ethoxyethylacrylate; C₆-C₄₀ arylalkyl acrylates (e.g., 2-phenylethyl acrylate,2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate,3-phenylpropyl acrylate, 4-phenylbutyl acrylate, 5-phenylpentylacrylate,

8-phenyloctyl acrylate, or 2-phenylethoxy acrylate; and C₆-C₄₀ arylalkylmethacrylates (e.g., 2-phenylethyl methacrylate, 3-phenylpropylmethacrylate, 4-phenylbutyl methacrylate,5-phenylpentyl methacrylate, 8-phenyloctyl methacrylate, 2-phenoxyethylmethacrylate, 3,3-diphenylpropyl methacrylate,2-(1-naphthylethyl)methacrylate, benzyl methacrylate, or2-(2-naphthylethyl)methacrylate.

Alternatively, the C₆-C₄₀ arylalkyl acrylates can be defined by thefollowing formula:

wherein: R is H or CH₃; m is 0-10;

Y is nothing, O, S, or NR wherein R is H, CH₃ or another lower alkyl,iso-OC₃H₇, phenyl or benzyl;

Ar is any aromatic ring, e.g., phenyl, which can be unsubstituted orsubstituted with H, CH₃, C₂H₅, n-C₃H₇, iso-C₃H₇, OCH₃, C₆H₁₁, Cl, Br orOH.

Reinforced cross-linked silicone elastomers can be prepared with thecrosslink agent of general formula I, or of general formula II, and ahydrophilic vinyl monomer. These silicon elastomers will include asiloxane polymer containing 12 to 18 mol percent of aryl substitutedsiloxane units of the formula R⁴R⁵—SiO. In the formula, R⁴ and R⁵ arethe same or different and represent phenyl, mono-lower alkyl substitutedphenyl groups, or di-lower alkyl substituted phenyl groups. Preferablyboth R⁴ and R⁵ are phenyl. The siloxane polymer will have end blockerscontaining siloxane units of the formula R¹R²R³—SiO₅ wherein R¹ and R²are alkyl, aryl or substituted alkyl or substituted aryl groups, and R¹and R² can be the same or different. The R group of the end blockingsiloxane units is an alkenyl group. Preferably, the end blocker is adimethylvinyl siloxane unit.

The balance of the polymer consists of dialkyl siloxane units of theformula R⁶R⁷—SiO wherein R⁶ and R⁷ are the same or different from andare methyl or ethyl groups, and the polymer has a degree ofpolymerization from 100 to 2000. Preferably, R⁶ and R⁷ are both methyl,and the degree of polymerization is approximately 250.

A trimethyl silyl treated silica reinforcer is finely dispersed in thepolymer, in a weight ratio of approximately 15 to 45 parts of thereinforcer to 100 parts of the polymer. Preferably, there isapproximately 27 parts of reinforcer to 100 parts of the copolymer.

Polymeric materials prepared with the crosslink agent of general formulaI, or of general formula II, and a hydrophilic vinyl monomer can beprepared by polymerizing the following monomeric components:

(A) 5% to 25% by weight of acrylate represented by the general formula

wherein Ar represents an aromatic ring of which hydrogen atom may besubstituted by a substitutional group, X represents an oxygen atom or adirect bonding, and m represents an integer from 1 to 5;

(B) 50% to 90% by weight of 2-hydroxyethyl(meth)acrylate; and

(C) 5% to 45% by weight of a (meth)acrylate monomer though not of theformula that represent monomer (A) and not 2-hydroxyethyl(meth)acrylate.Also, the coefficient of water absorption of the homopolymer of monomer(C) is not more than 30% by weight. The coefficient of water absorption(H₂O_(abs.) %) is defined as the following equation: H₂O_(abs.)%=[(W_(h)−W_(d))/W_(d)]×100

wherein the value is calculated at 25° C. by using a sample 1 mm thick;W_(h) represents a weight (g) of the sample in an equilibrium state withwater, and W_(d) represents a weight (g) of the sample in a dry state.The water content (% Water) is given by the following formula:

% Water=[(W _(h) −W _(d))/W _(h)]×100

An exemplary listing of (meth)acrylate monomer (C) include an alkyl(meth)acrylate containing a straight chain, a branched chain or cyclicchain such as methyl(meth)acrylate, ethyl(meth)acrylate,propyl(meth)acrylate, butyl(meth)acrylate, pentyl(meth)acrylate,hexyl(meth)acrylate, heptyl(meth)acrylate, nonyl(meth)acrylate, stearylmeth)acrylate, octyl(meth)acrylate, decyl(meth)acrylate,lauryl(meth)acrylate, pentadecyl(meth)acrylate,2-ethylhexyl(meth)acrylate, cyclopentyl(meth)acrylate, (meth)acrylate,cyclohexyl(meth)acrylate: an alkyl(meth)acrylate containing 1 to 5carbon atoms of alkyl group: a hydroxyalkyl(meth)acrylate containing astraight chain, a branched chain or cyclic chain, except for 2-HE(M)A(B), and any mixture thereof. Among the alkyl methacrylates thosecontaining 1 to 3 carbon atoms of alkyl group are preferred. Among thehydroxyalkyl methacrylates those containing 3 to 6 carbon atoms ofhydroxyalkyl group are preferred.

Polymeric materials can be prepared with a crosslink agent generalformula I, general formula II or general formula III, and a hydrophilicvinyl monomer by copolymerizing a specific monomer mixture comprisingperfluorooctylethyloxypropylene(meth)acrylate,2-phenylethyl(meth)acrylate, and an alkyl(meth)acrylate monomer havingthe following general formula,

wherein R is hydrogen or methyl and R¹ is a linear or branched C₄-C₁₂alkyl group. The perfluorooctylethyloxypropylene (meth)acrylate ispresent from 5% to 20% by weight, the 2-phenylethyl(meth)acrylate ispresent from 40% to 60% by weight, the alkyl(meth)acrylate monomer ispresent from 30% to 50% by weight and the crosslinking agent is presentfrom 0.5% to 4% by weight.

The above described polymeric materials are prepared by generallyconventional polymerization methods from the respective monomericcomponents. A polymerization mixture of the monomers in the selectedamounts is prepared. To this mixture is added a crosslink agent ofgeneral formula I, or of general formula II, at least one othercrosslink agent particularly suited for an acrylate-methacrylate- oracrylamide-based monomer and a conventional thermal free-radicalinitiator. The mixture is introduced into a mold of suitable shape toform the optical material and the polymerization initiated by gentleheating. Typical thermal, free radical initiators include peroxides,such as benzophenone peroxide, peroxycarbonates, such asbis-(4-t-butulcyclohexyl)peroxydicarbonate, azonitriles, such asazobisisobytyronitrile, and the like. A preferred initiator isbis-(4-t-butylcyclohexyl)peroxydicarbonate (PERK).

Alternatively, the monomers can be photopolymerized by using a moldwhich is transparent to actinic radiation of a wavelength capable ofinitiating polymerization of these acrylic monomers and crosslinkagents. Conventional photoinitiator compounds, e.g., a benzophenone-typephotoinitiator, can be introduced to facilitate thephoto-polymerization.

EXAMPLES Example 1 Preparation of 1,6-Hexanediol bis(N-vinyl carbamate)

A flame dried, 3-neck 250 mL round bottom flask (RBF) was fitted with aFriedrich reflux condenser (set to cool at 2.5° C.), a temperaturemonitoring probe and a 60 mL addition funnel with a pressure equalizingarm. The system was maintained under a slight N₂ pressure. To the RBFwere then charged 120 mL of anhydrous THF, 200 μL of dibutyltindilaurate (approx. 0.2% mol relative to OH groups) and 10 g of1,6-hexanediol (0.085 mol). The components were allowed to mix at roomtemperature.

To the 60 mL addition funnel (thoroughly dried with a flame torch) 15 gof N-vinyl isocyanate (0.217 mol) and 40 mL of anhydrous THF was addedvia syringe through a septum to prevent exposure to moisture. TheN-vinyl isocyanate in THF was slowly added to the RBF to preventexcessive heating as this reaction is fairly exothermic. Alternatively,the addition can be carried out at 0° C. to 5° C. by means of awater-ice bath. The addition of the N-vinyl isocyanate in THF isconducted over a 2 hr period. The contents of the RBF are slowly stirredat room temperature for 24 hrs over nitrogen. Removal of the solventprovides the product as a white powder that can be further dried byletting it sit under vacuum (20-30 mmHg) for 24-48 hrs. Typical yieldsrange from 95-99% by weight.

Example 2 Diethyleneglycol bis(N-vinyl carbamate)

A flame dried, 3-neck 250 mL round bottom flask (RBF) was fitted with aFriedrich reflux condenser (set to cool at 2.5° C.), a temperaturemonitoring probe and a 60 mL addition funnel with a pressure equalizingarm. The system was maintained under a slight N₂ pressure. To the RBFwere then charged 75 mL of anhydrous methylene chloride, 150 μL ofdibutyltin dilaurate (approx. 0.25% mol relative to OH groups) and 6 gof diethyleneglycol (0.0565 mol). The components were allowed to mix atroom temperature. To the 60 mL addition funnel (thoroughly dried with aflame torch) 10 g of N-vinyl isocyanate (0.145 mol) and 50 mL ofanhydrous methylene chloride was added via syringe through a septum toprevent exposure to moisture.

The N-vinyl isocyanate in methylene chloride was slowly added to the RBFto prevent excessive heating as this reaction is fairly exothermic.Alternatively, the addition can be carried out at 0° C. to 5° C. bymeans of a water-ice bath. The addition is conducted over a 2 hr period.The contents of the RBF are then slowly stirred at room temperature for24 hrs. Removal of the solvent provides the product as a white powderthat can be further dried by letting it sit under vacuum (20-30 mmHg)for 24-48 hrs. Typical yields range from 95-99% by weight. The productcan be purified by recrystallization from ethyl ether/hexane.

Example 3 Synthesis of 1,12-bis-(3-(-1-vinyl-2-pyrrolidinonyl)dodecane

The synthetic procedure described in White, et al., J. of PolymerScience Part A: Polymer Chemistry Vol. 40, 694-706, (2002) was followed.All glassware was oven dried at 160° C. prior to use.N-vinyl-2-pyrrolidinone (NVP) was distilled and placed over 4 Åmolecular sieves for 24 hrs before use. All other reagents were used asreceived from Aldrich chemical Co. A 250 ml, three-neck flask was fittedwith an addition funnel, an N₂ inlet, magnetic stirrer, rubber septumand thermocouple probe. The flask was charged with lithiumbis(trimethylsilyl)amide (LTMSA) 82 mL (1.0 molar solution in THF), 0.82mol and then stirred in a dry ice/acetone bath to about −76° C. NVP (9mL, 0.084 moles) in THF (9 mL) was added drop wise over approximately 30minutes. The reaction stirred for an additional 1 hr.1,12-dibromododecane (12.8 g, 0.039 moles) in 10 ml THF was added to thereaction flask drop wise. The mixture was stirred for 1 hr at less than−74° C. and then allowed to reach room temperature. Stirring continuedfor 48 hours. A sample was taken, quenched with water and extracted withether. GC analysis showed no evidence of 1,12-dibromododecane (I)remaining in the reaction mixture.

The reaction was quenched with 50 mL of purified water and the organiclayer was removed. The water layer was extracted 3×50 mL of ether; theorganic layers were combined and dried over magnesium sulfate. Flashevaporation provided 13.3 grams of crude material which was analyzed byGC-Mass spectroscopy and contained NVP monomer,1-(-3-vinyl-2-pyrrolidinonyl)-12-bromododecane and the desired product.The crude yield is 88%. The crude material was purified by silica gelcolumn chromatography using ethylacetate/heptane (70/30) as an elutingsolvent. Fractions I and II appeared to contain the major product. Thefirst fraction was 6.1 grams, of viscous oil and the second fraction was3.05 grams of a semisolid.

Examples 4 and 5 Preparation of a Silicon Hydrogels

Silicon hydrogel materials were prepared from the polymerizationmixtures listed in Table 2. The polymerization reaction was conductedusing methods well known by those of ordinary skill in the art. Thevinyl crosslink agent used in the polymerization was1,6-hexanediol-bis-(N-vinyl carbamate), and is reported in weightpercent based on the total weight of the polymerization mixture. M2D39is diquat, siloxane monomer shown below, and Tris istris-(trimethylsiloxy)-3-methacryloxypropylsilane.

TABLE 2 Component (parts) Ex. 4 Ex. 5 Comp. Ex. 1 M2D39 9.3 9.3 9.3 Tris23.25 23.25 23.25 NVP 41.85 41.85 41.85 HEMA 18.6 18.6 18.6 Propyleneglycol 5 5 5 AIBN 0.5 0.5 0.5 vinyl crosslink (wt %) 0.5 1.0 0

The silicon hydrogel films of Table 2 were dried released from theirrespective molds and weighed. The films were then extracted with waterovernight, or with isopropanol overnight (approximately 16 hrs) or for 2hrs. The extracted films were then dried at 100° C. for 18-24 hrs atreduced pressure (30 mmHg) and the dry weight recorded. Table 3summarizes the weight percent of the extracted compounds from the films,which includes the diluent, propylene glycol.

TABLE 3 Example water (16 hrs) IPA (16 hrs) IPA (2 hrs) 4 7.11 9.83 4.375 6.05 9.66 3.77 Comp. 1 11.29 14.16 13.16

Examples 6A to 6C Preparation of a Silicon Hydrogels

Silicon hydrogel materials were prepared from the polymerizationmixtures listed in Table 4. The polymerization reaction was conductedusing methods well known by those of ordinary skill in the art. Thevinyl crosslink agent used in the polymerization was1,6-hexanediol-bis-(N-vinyl carbamate), and is reported in weightpercent based on the total weight of the polymerization mixture. Thesilicon hydrogel films were dried released from their respective moldsand weighed. The films were then extracted as indicated in Table 3. Theextracted films were then dried at 100° C. for 18-24 hrs at reducedpressure (30 mmHg) and the dry weight recorded. The polymerization andsubsequent extraction for each formulation was repeated five times. Theextraction data is also reported in Table 4 with the standard deviationfor the repeated experiments.

Examples 7A to 7C. Preparation of a Silicon Hydrogels

Silicon hydrogel materials were prepared from the polymerizationmixtures listed in Table 5. The polymerization reaction was conductedusing methods well known by those of ordinary skill in the art. Thevinyl crosslink agent used in the polymerization was diethyleneglycol-bis-(N-vinyl carbamate), and is reported in weight percent basedon the total weight of the polymerization mixture.

The silicon hydrogel films of Table 5 were dried released from theirrespective molds and weighed. The films were then extracted withisopropanol for 2 hrs. The extracted films were then dried at 100° C.for 18-24 hrs at reduced pressure (30 mmHg) and the dry weight recorded.The polymerization and subsequent extraction for each formulation wasrepeated five times. The extraction data is also reported in Table 5with the standard deviation for the repeated experiments.

TABLE 4 Component (parts) Ex. 6A Ex. 6B Ex. 6C Comp. Ex. 2 M2D39 5.3 5.35.3 5.3 M1D11 4.0 4.0 4.0 4.0 Tris 23.25 23.25 23.25 23.25 NVP 41.8541.85 41.85 41.85 HEMA 18.6 18.6 18.6 18.6 Propylene glycol 5.0 5.0 5.05.0 AIBN 0.5 0.5 0.5 0.5 Ex. 2 (wt %) 0.2 0.3 0.5 0 extraction wt % 8.7± 0.26 8.3 ± 0.26 7.5 ± 0.2 13.5 ± 4.5

M1D11 is a monomethacrylate ester of Gelest MCR-C12 having the generalformula below.

Examples 8A to 8D Preparation of a Silicon Hydrogels

Silicon hydrogel materials were prepared from the polymerizationmixtures listed in Table 6. The polymerization reaction was conductedusing methods well known by those of ordinary skill in the art. Thevinyl crosslink agent used in the polymerization was diethyleneglycol-bis-(N-vinyl carbamate), and is reported in weight percent basedon the total weight of the polymerization mixture.

The silicon hydrogel films of Table 6 were dried released from theirrespective molds and weighed. The films were then extracted withisopropanol for 2 hrs. The extracted films were then dried at 100° C.for 18-24 hrs at reduced pressure (30 mmHg) and the dry weight recorded.The polymerization and subsequent extraction for each formulation wasrepeated five times. The extraction data is also reported in Table 6with the standard deviation for the repeated experiments.

TABLE 5 Component (parts) Ex. 7A Ex. 7B Ex. 7C M2D39 5.3 5.3 5.3 M1D114.0 4.0 4.0 Tris 23.25 23.25 23.25 NVP 41.85 41.85 41.85 HEMA 18.6 18.618.6 Propylene glycol 5.0 5.0 5.0 AIBN 0.5 0.5 0.5 Ex. 2 (wt %) 0.2 0.30.5 extraction wt % 8.9 ± 0.72 8.4 ± 0.5 8.1 ± 1.2

The mechanical properties of the resulting hydrogel films of Examples 9Ato 9D are listed in Table 7. The formulation of Comparative Example 3resulted in a weak, fragile material, which could not be mechanicallytested, and thus, is not a suitable optical material.

TABLE 6 Component (parts) Ex. 8A Ex. 8B Ex. 8C Ex. 8D Comp. Ex. 3 M2D254.5 4.5 4.5 4.5 17.1 Tris 44.0 44.0 30.0 25.0 31.9 NVP 19.0 19.0 30.025.0 21.0 DMA 3.0 3.0 6.0 15.0 — hexanol 28.7 28.2 28.7 29.7 29.7Darocure 1173 0.3 0.3 0.3 0.3 0.3 Ex. 2 (wt %) 0.5 1.0 0.5 0.5 0 M2D25is α,ω-bis(methacryloxybutyl polydimethylsiloxane with DP = 25

TABLE 7 modulus tensile elongation Tear Example appearance (g/mm²)(g/mm²) % g/mm 8A clear 305 ± 46 116 ± 28 176 ± 26 26 ± 3 8B clear 299 ±35 132 ± 16 157 ± 15 35 ± 9 8C clear 83 ± 3  50 ± 18  94 ± 38  5 ± 1 8Dclear 52 ± 4  26 ± 17  72 ± 52   2 ± 0.5

Examples 9A to 9D Preparation of a Silicon Hydrogels

The silicon hydrogel films of Table 8 were dried released from theirrespective molds and weighed. The films were then extracted withisopropanol for 2 hrs. The extracted films were then dried at 100° C.for 18-24 hrs at reduced pressure (30 mmHg) and the dry weight recorded.The polymerization and subsequent extraction for each formulation wasrepeated five times.

The mechanical properties of the resulting hydrogel films of Examples 9Ato 9D are listed in Table 9.

TABLE 8 Component (parts) Ex. 9A Ex. 9B Ex. 9C Ex. 9D VCa1D11 22 22 2222 Tris 7.5 15 20 30 NVP 30.5 30.5 30.5 30.5 HEMA 8.6 8.6 8.6 8.6 TEGDMA2 3 3 3 Ex. 2 0.3 0.3 0.3 0.3 Darocure 1173 0.3 0.3 0.3 0.33-Me-3-pentanol 41.5 41.5 41.5 41.5 VCa1D11 is a siloxane macromer offormula below

TABLE 9 Dk modulus tensile Tear water Example clarity Barrers (g/mm²)(g/mm²) elongation % g/mm content 9A clear 44 89 ± 16 31 ± 9  53 ± 16 <250.7 9B clear 69 104 ± 7  49.8 ± 16   84 ± 18 3 ± 0.5 44.1 9C clear 70115 ± 6  50 ± 20 73 ± 32 3 ± 0.5 39.5 9D clear 85 98 ± 26 43 ± 10 96 ±29 5 ± 1   34.2

Examples 10A to 10E Preparation of a Silicon Hydrogels

The silicon hydrogel films of Table 10 were dried released from theirrespective molds and weighed. Each component is listed by percent byweight of the polymerization mixture. The films were then extracted withisopropanol for 2 hrs. The extracted films were then dried at 100° C.for 18-24 hrs at reduced pressure (30 mmHg) and the dry weight recorded.The polymerization and subsequent extraction for each formulation wasrepeated five times.

The mechanical properties of the resulting hydrogel films of Examples10A to 10E are listed in Table 11.

TABLE 10 Component (parts) Ex. 10A Ex. 10B Ex. 10C Ex. 10D Ex. 10EVCa1D11 — 10 — 7.5 — M1-MCR-C12 10 — 10 — — VC1D11 — — — — 7.5 Tris 4040 35 36 36 NVP 35 35 30 44.4 44.4 DMA 5 5 5 3 3 HEMA — — 10 — — Ma2D3710 10 10 9 9 Ex. 2 0.3 0.3 0.3 0.15 0.15 Darocure 1173 0.5 0.5 0.5 0.40.4 hexanol 20 20 20 20 20

VC1D11 and M1-MCR-C12 are siloxane macromers of formula below

TABLE 11 modulus tensile Tear water Example clarity Dk Barrers (g/mm²)(g/mm²) elongation % g/mm content 10A clear 96 50 ± 10 — — 5 40.4 10Bclear 89 87 ± 9  — — 5 48.3 10C clear 79 68 ± 6  56 ± 14 143 ± 38 5 ±1   47 10D clear 83 73 ± 12 50 ± 21 117 ± 45 4 ± 0.5 55.4 10E clear 7690 ± 10 65 ± 4  140 ± 8  4 ± 0.2 53.3

1. A compound of general formula I

wherein R¹, R², R³, R⁴, R⁷ and R⁸ are independently selected fromhydrogen, C₁-C₄alkyl, C₁-C₂alkanol or hydroxyl; A is O, O(CH₂CH₂O)_(v)or [SiR⁵R⁶O]_(w)SiR₅R⁶, wherein R⁵ and R⁶ are independently selectedfrom C₁₋₄alkyl or phenyl, and v is from 1-20 and w is from 0 to 60; mand n are integers independently selected from 1 to 10; p is 0 or 1; andq is an integer from 0 to 6; and X and Y are independently selected fromO or NR⁹, wherein R⁹ is hydrogen, C₁-C₄alkyl or C₁-C₂alkanol.
 2. Thecompound of claim 1 wherein Y is NR⁹ and X is O.
 3. The compound ofclaim 1 wherein Y is O and X is NR⁹.
 4. The compound of claim 1 whereinY is NR⁹ and X is NR⁹.
 5. The compound of claim 1 wherein m and n are 2or 3, p is 0, and R¹, R², R³ and R⁴ are hydrogen.
 6. The compound ofclaim 5 wherein q is 0, 1 or 2, Y is O and X is NR⁹.
 7. A compound ofgeneral formula II

wherein R¹, R², R³, R⁴, R⁷ and R⁸ are independently selected fromhydrogen, C₁-C₄alkyl, C₁-C₂alkanol or hydroxyl; A is O, O(CH₂CH₂O)_(v)or [SiR⁵R⁶O]_(w)SiR⁵R⁶, wherein R⁵ and R⁶ are independently selectedfrom C₁₋₄alkyl or phenyl, and v is from 1-20 and w is from 0 to 60; mand n are integers independently selected from 1 to 10; p is 0 or 1; andq is an integer from 0 to
 6. 8. The compound of claim 7 wherein m and nare 2 or 3, p is 0, q is 0, 1 or 2 and R¹, R², R³ and R⁴ are hydrogen.9. The use of the compound of claim 1 as a crosslink agent for thecopolymerization of a hydrophilic monomer, wherein the hydrophilicmonomer has a reactivity ratio R_(h)=k_(hh)/k_(hx) and the compound ofclaim 1 has a reactivity ratio R_(x)=k_(xx)/k_(xh), wherein k_(hh),k_(hx), k_(xx) and k_(xh) are the propagation constants for thefollowing radical polymerization reactions, and M_(h) represents thehydrophilic monomer, M_(h)* represents the hydrophilic monomer radical,M_(x) represents the crosslink agent, and M_(x)* represents thecrosslink agent radical,M _(h) *+M _(h) →M _(h) M _(h) *k _(hh);M _(h) *+M _(x) →M _(h) M _(x) *k _(hx);M _(x) *+M _(x) →M _(x) M _(v) *k _(xx);M _(x) *+M _(h) →M _(x) M _(h) *k _(xh); and the ratio R_(h)/R_(x) isfrom 0.1 to
 10. 10. The use of the compound of claim 9 wherein thehydrophilic monomer is selected from the group consisting of N-vinylpyrrolidone, N-vinyl piperidone, N-vinyl-ε-caprolactam,N-vinylimidazolidone, N-vinylsuccinimide, N-vinylformamide and mixturesthereof.
 11. The use of the compound of claim 1 as a crosslink agent forthe copolymerization of a hydrophilic monomer selected from the groupconsisting of N-vinyl pyrrolidone, N-vinyl piperidone,N-vinyl-ε-caprolactam, N-vinylimidazolidone, N-vinylsuccinimide,N-vinylformamide and mixtures thereof, wherein the compound of claim 1and the hydrophilic monomer is included in a polymerization mixture thatalso includes a crosslink agent for a lens monomer, wherein the lensmonomer is selected from the group consisting of 2-hydroxyethylmethacrylate, tris-(trimethylsiloxy)-3-methacryloxypropylsilane,dimethylacrylamide, ethylene glycol dimethacrylate, methacrylic acid,2-phenylethyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethylmethacrylate, triethylene glycol dimethacrylate, tetraethylene glycoldimethacrylate, isobornyl methacrylate, 2-methoxyethyl methacrylate,glycerol methacrylate, monomethoxy polyethyleneglycol methacrylate andany mixture thereof.
 12. The use of the compound of claim 9 in thepreparation of an ophthalmic lens.
 13. The use of the compound of claim10 in the preparation of an ophthalmic lens.
 14. A polymer comprisingthe reaction product of two or more crosslink agents, a hydrophilicmonomer and a lens monomer, wherein at least one of the crosslink agentsis of general formula I

wherein R¹, R², R³, R⁴, R⁷ and R⁸ are independently selected fromhydrogen, C₁-C₄alkyl, C₁-C₂alkanol or hydroxyl; A is O, O(CH₂CH₂O)_(v)or [SiR⁵R⁶O]_(w)SiR⁵R⁶, wherein R⁵ and R⁶ are independently selectedfrom C₁₋₄alkyl or phenyl, and v is from 1-20 and w is from 0 to 60; mand n are integers independently selected from 1 to 10; p is 0 or 1; andq is an integer from 0 to 6; and X and Y are independently selected fromO or NR⁹, wherein R⁹ is hydrogen, C₁-C₄alkyl or C₁-C₂alkanol.
 15. Thepolymer of claim 14 wherein the hydrophilic monomer is selected from thegroup consisting of N-vinyl pyrrolidone, N-vinyl piperidone,N-vinyl-1-caprolactam, N-vinylimidazolidone, N-vinylsuccinimide,N-vinylforamide and mixtures thereof.
 16. The polymer of claim 14wherein the hydrophilic monomer is N-vinyl pyrrolidone.
 17. The polymerof claim 15 wherein the lens monomer is selected from the groupconsisting of 2-hydroxyethyl methacrylate,tris-(trimethylsiloxy)-3-methacryloxypropylsilane, dimethylacrylamide,ethylene glycol dimethacrylate, methacrylic acid, 2-phenylethylacrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate,triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate,isobornyl methacrylate, 2-methoxyethyl methacrylate, glycerolmethacrylate, monomethoxy polyethyleneglycol methacrylate and anymixture thereof.
 18. The polymer of claim 14 wherein the hydrophilicmonomer has a reactivity ratio R_(h)=k_(hh)/k_(hx) and the crosslinkagent of formula I has a reactivity ratio R_(x)=k_(xx)/k_(xh), whereink_(hh), k_(hx), k_(xx) and k_(xh) are the propagation constants for thefollowing radical polymerization reactions, and M_(h) represents thehydrophilic monomer, M_(h)* represents the hydrophilic monomer radical,M_(x) represents the crosslink agent, and M_(x)* represents thecrosslink agent radical,M _(h) *+M _(h) →M _(h) M _(h) *k _(hh);M _(h) *+M _(x) →M _(h) M _(x) *k _(hx);M _(x) *+M _(x) →M _(x) M _(v) *k _(xx);M _(x) *+M _(h) →M _(x) M _(h) *k _(xh); and the ratio R_(h)/R_(x) isfrom 0.1 to
 10. 19. An ophthalmic lens comprising the polymer of claim18.
 20. A polymer comprising the reaction product of two or morecrosslink agents, a hydrophilic vinyl monomer and a lens monomer,wherein at least one of the crosslink agents is of general formula II

wherein R¹, R², R³, R⁴, R⁷ and R⁸ are independently selected fromhydrogen, C₁-C₄alkyl, C₁-C₂alkanol or hydroxyl; A is O, O(CH₂CH₂O)_(v)or [SiR⁵R⁶O]_(w)SiR⁵R⁶ wherein R⁵ and R⁶ are independently selected fromC₁-C₄alkyl or phenyl, and v is from 1-20 and w is from 0 to 60; m and nare integers independently selected from 1 to 10; p is 0 or 1; and q isan integer from 0 to
 6. 21. The polymer of claim 20 wherein thehydrophilic monomer has a reactivity ratio R_(h)=k_(hh)/k_(hx) and thecrosslink agent of formula II has a reactivity ratioR_(x)=k_(xx)/k_(xh), wherein k_(hh), k_(hx), k_(xx) and k_(xh) are thepropagation constants for the following radical polymerizationreactions, and M_(h) represents the hydrophilic monomer, M_(h)*represents the hydrophilic monomer radical, M_(x) represents thecrosslink agent, and M_(x)* represents the crosslink agent radical,M _(h) *+M _(h) →M _(h) M _(h) *k _(hh);M _(h) *+M _(x) →M _(h) M _(x) *k _(hx);M _(x) *+M _(x) →M _(x) M _(v) *k _(xx);M _(x) *+M _(h) →M _(x) M _(h) *k _(xh); and the ratio R_(h)/R_(x) isfrom 0.1 to
 10. 22. The polymer of claim 20 wherein the hydrophilicmonomer is selected from the group consisting of N-vinyl pyrrolidone,N-vinyl piperidone, N-vinyl-ε-caprolactam, N-vinylimidazolidone,N-vinylsuccinimide, N-vinylformamide and mixtures thereof.
 23. Thepolymer of claim 22 wherein the lens monomer is selected from the groupconsisting of 2-hydroxyethyl methacrylate,tris-(trimethylsiloxy)-3-methacryloxypropylsilane, dimethylacrylamide,ethylene glycol dimethacrylate, methacrylic acid, 2-phenylethylacrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate,triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate,isobornyl methacrylate, 2-methoxyethyl methacrylate, glycerolmethacrylate, monomethoxy polyethyleneglycol methacrylate and anymixture thereof.
 24. An ophthalmic lens comprising the polymer of claim21.
 25. A polymer comprising the reaction product of two or morecrosslink agents, a hydrophilic monomer and a lens monomer, wherein atleast one of the crosslink agents is of general formula III

wherein R¹ and R² are independently selected from hydrogen, C₁-C₄alkyl,C₁-C₂alkanol or hydroxyl; A is O, O(CH₂CH₂O)_(v) or [SiR⁵R⁶O]_(w)SiR⁵R⁶,wherein R⁵ and R⁶ are independently selected from C₁-C₄alkyl or phenyl,and v is from 1-20 and w is from 0 to 60; m is 1, 2 or 3; n and n′ areintegers independently selected from the integers 1 to 10; and p is 0or
 1. 26. The polymer of claim 25 wherein the hydrophilic monomer has areactivity ratio R_(h)=k_(hh)/k_(hx) and the crosslink agent of formulaIII has a reactivity ratio R_(x)=k_(xx)/k_(xh), wherein k_(hh), k_(hx),k_(xx) and k_(xh) are the propagation constants for the followingradical polymerization reactions, and M_(h) represents the hydrophilicmonomer, M_(h)* represents the hydrophilic monomer radical, M_(x)represents the crosslink agent, and M_(x)* represents the crosslinkagent radical,M _(h) *+M _(h) →M _(h) M _(h) *k _(hh);M _(h) *+M _(x) →M _(h) M _(x) *k _(hx);M _(x) *+M _(x) →M _(x) M _(v) *k _(xx);M _(x) *+M _(h) →M _(x) M _(h) *k _(xh); and the ratio R_(h)/R_(x) isfrom 0.1 to
 10. 27. The polymer of claim 25 wherein the hydrophilicmonomer is selected from the group consisting of N-vinyl pyrrolidone,N-vinyl piperidone, N-vinyl-ε-caprolactam, N-vinylimidazolidone,N-vinylsuccinimide, N-vinylformamide and mixtures thereof.
 28. Thepolymer of claim 27 wherein the lens monomer is selected from the groupconsisting of 2-hydroxyethyl methacrylate,tris-(trimethylsiloxy)-3-methacryloxypropylsilane, dimethylacrylamide,ethylene glycol dimethacrylate, methacrylic acid, 2-phenylethylacrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate,triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate,isobornyl methacrylate, 2-methoxyethyl methacrylate, glycerolmethacrylate, monomethoxy polyethyleneglycol methacrylate and anymixture thereof.
 29. An ophthalmic lens comprising the polymer of claim26.
 30. The polymer composition of claims 9, 18, 21 or 26 wherein thehydrophilic monomer and the lens monomer have a reactivity ratio,R_(H)/R_(L), greater than 10 or less than 0.1, the reactivity ratio,R_(H)/R_(L), defined the following radical polymerization reactions,wherein M_(h) represents the hydrophilic monomer, M_(h)* represents thehydrophilic monomer, M_(l) represents the lens monomer, M_(l)*represents the lens monomer radical, M_(i) represents the crosslinkagent, and M_(i)* represents the crosslink agent radical,M _(h) *+M _(h) →M _(h) M _(h) *k _(hh);M _(h) *+M _(i) →M _(h) M _(i) *k _(hi);M _(i) *+M _(i) →M _(i) M _(i) *k _(ii);M _(i) *+M _(h) →M _(i) M _(h) *k _(ih); and R_(H) is R_(h)/R_(i),andM _(l) *+M _(l) →M _(l) M _(l) *k _(ll);M _(l) *+M _(i) →M _(l) M _(i) *k _(li);M _(i) *+M _(i) →M _(i) M _(i) *k _(ii);M _(i) *+M _(l) →M _(i) M _(l) *k _(il); and R_(L) is R_(l)/R_(i).